Correcting the z ∼ 8 galaxy luminosity function for gravitational lensing magnification bias
- Department of Physics, University of California, Santa Barbara, CA, 93106-9530 (United States)
- Institute of Astronomy, University of Cambridge, Madingley Rd, Cambridge, CB3 0HA (United Kingdom)
- Kavli Institute for Cosmology and Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA (United Kingdom)
- Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, 452 Lomita Mall, Stanford, CA 94035 (United States)
- School of Physics, University of Melbourne, Parkville, Victoria (Australia)
- Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD, 21218 (United States)
We present a Bayesian framework to account for the magnification bias from both strong and weak gravitational lensing in estimates of high-redshift galaxy luminosity functions (LFs). We illustrate our method by estimating the z ∼ 8 UV LF using a sample of 97 Y-band dropouts (Lyman break galaxies) found in the Brightest of Reionizing Galaxies (BoRG) survey and from the literature. We find the LF is well described by a Schechter function with characteristic magnitude of M{sup ⋆}=−19.85{sub −0.35}{sup +0.30}, faint-end slope of α=−1.72{sub −0.29}{sup +0.30}, and number density of log{sub 10}Ψ{sup ⋆}(Mpc{sup −3})=−3.00{sub −0.31}{sup +0.23}. These parameters are consistent within the uncertainties with those inferred from the same sample without accounting for the magnification bias, demonstrating that the effect is small for current surveys at z ∼ 8, and cannot account for the apparent overdensity of bright galaxies compared to a Schechter function found recently by Bowler et al. and Finkelstein et al. We estimate that the probability of finding a strongly lensed z ∼ 8 source in our sample is in the range ∼3–15% depending on limiting magnitude. We identify one strongly lensed candidate and three cases of intermediate lensing in BoRG (estimated magnification μ > 1.4) in addition to the previously known candidate group-scale strong lens. Using a range of theoretical LFs we conclude that magnification bias will dominate wide field surveys—such as those planned for the Euclid and WFIRST missions—especially at z > 10. Magnification bias will need to be accounted for in order to derive accurate estimates of high-redshift LFs in these surveys and to distinguish between galaxy formation models.
- OSTI ID:
- 22883171
- Journal Information:
- Astrophysical Journal, Vol. 805, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Since 2009, the country of publication for this journal is the UK.; ISSN 0004-637X
- Country of Publication:
- United Kingdom
- Language:
- English
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